601 FXUS66 KPQR 082237 CCA AFDPQR Area Forecast Discussion...CORRECTED National Weather Service Portland OR 328 PM PDT Fri Oct 8 2021 .SYNOPSIS...Generally fair and fall-like weather Saturday will be replaced by wet and cooler weather Sunday. Weak ridging attempts to bring a break in rain chances for early next weak, before rain chances increase again by mid-week. && .SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT...A couple light sprinkles continue across the central coast at this time, but models suggest this will continue to decrease in coverage and intensity throughout the evening as subsiding, drier air filters in from the west. Tonight, with few to no clouds early on, some patchy fog may develop in low-lying areas, but model soundings from the NAM (which has a tendency to overmoisten the boundary layer) suggest it will be difficult to saturate at and near the surface, with dewpoint depressions generally 2F or more. The HREF suggests chances for low cloud development increase in the early morning (around 6-9 AM), and then continue for much of the day Saturday. Meanwhile, forecast soundings from the NAM and GFS suggest instability doesn't show up until around 11 AM. Suspect the HREF is hinting at the potential for a weak marine push making it into the Willamette Valley by around sunrise (though it only has 10-30% chances in the Willamette Valley), and thereafter thinks cumuliform clouds will pop up during the day in the unstable, post cold-frontal airmass. Tomorrow should be a pleasant, fall-like day with high temperatures across the Willamette Valley in the low 60s with generally light southerly winds. With an onshore flow component and a few more clouds around, it may be even cooler along the coast, with highs likely only in the mid to upper 50s. Saturday night, a cold front approaches from the northwest. Ahead of it, stratus and chances for rain increase beginning around 2 PM Saturday along the northwest Oregon and southwest Washington coasts, and after around 7 PM in the northern Willamette Valley. With the arrival of the cold front late Saturday night/early Sunday morning, winds will increase along the coast, and will rapidly back from south-southwesterly to northwesterly with gusts to 30 mph possible. Steady rain will also come to an end with the passage of the front Sunday morning, with a showery pattern taking over thereafter. The NBM suggests 6 hour thunder chances will be in the 20-25% range from both 5 PM to 11 PM and 11 PM to 5 AM Sunday into Monday along the coast. The SREF's 3 hour thunder probabilities throughout the same time period are about the same, though there is more variability in the SREF given its higher-resolution model composition. It suggests the highest chances for thunder, in excess of 25% during the 8-11 PM timeframe Sunday evening, will be along the coast and in the Coast Range generally between Lincoln City and Astoria, while lower chances of ~5-15% extend further north and south along the coast. Not overly confident, at this time, in the high spatial resolution the SREF is giving, but the signal for heightened thunder chances in the areas it's delineating is there. These model forecasts for thunder chances are also in-line with what forecast soundings suggest: Strong unidirectional wind shear and marginal instability that extends up to around 500mb. For this, a slight chance of thunder has been added to the forecast for the Coast and Coast Range from 5 PM Sunday through 5 AM Monday. Sunday should not be a day of continual rain, but rather isolated to scattered showers with some breaks of sunshine, especially later in the day. It should wind up being a pretty cool day, with NBM suggesting the chances for exceeding 60F at PDX are only around 20%. While NBM is currently forecasting highs in only the mid to upper 50s in the Willamette Valley on Sunday, temperatures may ultimately climb a few degrees more if sufficient breaks of sunshine can occur. Temperatures on Sunday will also depend on how many (and if any) heavier showers occur during the late-morning through evening timeframe, as these will be vertically built and will carry the potential to bring some pretty cold rain down to cool the lower atmosphere by evaporation. -Bumgardner && .LONG TERM...MONDAY THROUGH THURSDAY...WPC's cluster analysis suggests good agreement between models and their ensembles in the synoptic-scale pattern during the first half of the long-term, with a weak ridge that attempts to build in on Tuesday getting pulled southeast and subsequently replaced by weak troughing and northwesterly flow on the back side of the closed low in the Four Corners. However, it also suggests discrepancies thereafter, with two clusters suggesting zonal flow and the remaining two suggesting ridging by the end of the period. The deterministic GFS and ECMWF suggest a short wave will traverse the Pacific Northwest during the Tuesday night into Wednesday timeframe. With this disturbance, some light precipitation amounts are expected yet again. A few showers may stick around on Wednesday - especially early in the day - but it is not looking to be a total washout at this time. The remainder of the long term period is currently looking to be precipitation-free for now, with temperatures near seasonal averages for this time of year. Overall, next week, not unlike this past week, is looking fall-like in terms of both temperatures and precipitation. -Bumgardner && .AVIATION...The upper level trough continues to push southeast leaving a stalled low level front offshore. Mid level clouds along the coast will continue to break up into this evening as the front falls apart. Weak high pressure will build in behind the trough keeping the region in VFR criteria throughout the TAF period. Winds will be fairly light shifting from a northwesterly regime to a southerly pattern by Sunday afternoon. Weak winds and clearing skies will precondition the area for patchy fog/low stratus development overnight. Potential for MVFR ceilings along the coast after 12Z Saturday as another front approaches the coast. For detailed regional Pac NW aviation weather information, go online to: https://weather.gov/zse KPDX AND APPROACHES...VFR conditions will continue overnight with light northwesterly winds. Patchy fog is possible between 09 and 15Z. -BMuhlestein && .MARINE...As of 1 PM Friday the front is roughly 80 nm offshore and is nearly parallel to the coastline. With little forcing from winds aloft the front has essentially stalled offshore. Buoy 89 is still reporting gusts near 25 kt just ahead of the front. Although Buoy 50 has been just below SCA thresholds it's likely that wind gusts at or above 21 kt are occurring to the west roughly 50 nm offshore. The SCA has been extended until 11 PM this evening. The front will likely come onshore overnight which could bring some localized gusty conditions to the inner waters but impacts are not expected to be widespread. Wave heights will continue to be in the 4 to 6 ft range. Southerly winds will start to ramp up again Saturday afternoon as another front drops south across the waters. Ensembles from both the GEFS and ECMWF are continuing to show potential for wind gusts between 30 to 35 kt at Buoy 89 and Buoy 29 ahead of the front. Current model guidance is showing the front moving across the coastal waters between 2 AM and 5 AM Sunday. Winds will continue to be in the 20 to 25 kt range in the post-frontal environment through Sunday night. -BMuhlestein && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 11 PM PDT this evening for coastal waters from Cape Shoalwater WA to Florence OR from 10 to 60 nm. $$